Thief and Thief 2 are definitely worth a try if pure stealth gameplay appeals to you. Of particular note is that some anonymous person has just released an unofficial engine update for both games. The changes the update brings are mostly of interest to modders, which is great because the game still has an active modding community. There's also an amped-up version of the original demo for Thief 1 showing off the new stuff, which also gives you a hint about whether you want to drop $8 for the games. http://www.ttlg.com/forums/showthread.php?t=140085 has all of the details.